Jitter is the deviation from a true periodicity of a presumed periodic signal in electronics and telecommunications, often in relation to a reference clock source. Jitter can be observed in characteristics such as a frequency of successive pulses, a signal amplitude, or a phase of periodic signals. Jitter is a significant, and usually undesired, factor in the design of communications links. Jitter can be quantified in the same terms as all time-varying signals, e.g., root mean square (RMS), or peak-to-peak displacement. Also like other time-varying signals, jitter can be expressed in terms of spectral density (frequency content).
Jitter period is the interval between two times of maximum effect (or minimum effect) of a signal characteristic that varies regularly with time, and jitter frequency is its inverse. Jitter may be caused by electromagnetic interference (EMI) and crosstalk with carriers of other signals. Jitter can cause a display monitor to flicker, affect the performance of processors in personal computers, introduce clicks or other undesired effects in audio signals, and loss of transmitted data between network devices. The amount of tolerable jitter depends on the affected application.
In the context of computer networks, jitter is the variation in latency as measured in the variability over time of the packet latency across a network. Packet jitter is expressed as an average of the deviation from the network mean latency and is an important quality of service factor in assessment of network performance.
Jitter buffers or de-jitter buffers can be used to counter jitter introduced by queuing in packet switched networks so that a continuous play out of audio (or video) transmitted over the network can be ensured. The maximum jitter that can be countered by a de-jitter buffer is equal to the buffering delay introduced before starting the play-out of the media stream.
The above-described background relating to an adaptive dejitter buffering is merely intended to provide a contextual overview of some current issues, and is not intended to be exhaustive. Other contextual information may become further apparent upon review of the following detailed description.